Fluid jet filament intermingling devices have long been used to make twist-free coherent yarns and also to combine a plurality of yarns into a single coherent yarn having the filaments of the various yarns intermingled with one another. Most such interlacing or entangling patents show the yarn being guided straight through the center of the fluid jet device, and even where it is taught to bend the yarn at guides before and after the jet, the yarn is still centered in the jet as it moves through the yarn passageway of the jet.
Other patents describe jet designs aimed at achieving improved entanglement by bending the yarn at one location in or on the jet itself, and still others show the yarn bending in opposite directions at the jet entrance and exit. The orifice in these jets is typically centered with respect to the yarn passageway. Although useful in the production of a variety of different yarns, these jets do not produce consistently uniform intermingling. Lack of uniformity is a serious drawback when intermingling two or more yarns of different color or dyeability to make products of blended shades known as heather yarns.
A different type of intermingling device is shown in U.S. Pat. No. 4,505,013 (Nelson) wherein yarn approaching an entangling jet is enclosed in a tube to constrain lateral vibrations of the yarn. While the latter device is quite effective, the yarn cannot be strung up through the device while the yarn is running. In addition, the only means of selectively varying the degree of intermingling is to adjust the fluid pressure which also affects the uniformity of intermingling. A jet which can overcome these problems and produce heather yarns with consistently uniform intermingling would be highly desirable.